I think you might find that those are sites that have bad credentials and are auto-filtered because of it. I went to school pre-internet so I never had those restrictions (yes, there was a time like that where we used paper maps like pirates.) but I would also suggest that the people to which you will be speaking are stuck in the same box as you as they are required to use the software too and to rigidly follow the rules. As such, they are likely not to blame for the software or its application. If you consider their feelings they will likely consider yours.
I believe your school board or administration is responsible for the software choice and if, after exhausting your work with the IT department, you decide to approach them about it that a level headed proposal written in a scholarly manner will carry more weight than any verbal argument that you can pose.